This application claims the priority of Japanese Patent Applications No. 8-299712 filed on Oct. 23, 1996 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a light source device for an endoscope which is capable of shading illuminating light for a predetermined period and the structure of an electronic endoscope for medical and industrial use which is provided with such a light source device.
2. Description of the Related Art
An endoscope is an apparatus for irradiating illuminating light from a light source into an object of observation such as a body cavity so as to observe the interior of the object. A CCD (Charge Coupled Device) is mainly used as an image sensor. In the CCD, a video signal is obtained by reading an electric charge stored for each pixel by a photoelectric transducer, and it is possible to display the image of the interior of the object of observation by processing the video signal.
When a video signal is read out of the CCD, a pixel mixture signal reading method, for example, is adopted.
In the pixel mixture signal reading method, the charges stored in the CCD during an exposure of 1/60 sec (vertical scanning period) are read while the upper and lower picture data are added, and these signals form one field picture.
In the pixel mixture signal reading method, however, since the upper and lower pixel data are added and mixed, as described above, the resolution in the vertical direction is approximately 1/2. That is the vertical resolution is lowered. In addition, since the field information in the odd and even fields obtained every 1/60 sec constitute one frame picture (1/30 sec), if a blur is caused by a movement of the object or the endoscope itself, the picture quality is unfavorably deteriorated.